Bayesian inverse modeling and source location of an unintended <sup>131</sup>I release in Europe in the fall of 2011
In the fall of 2011, iodine-131 (<sup>131</sup>I) was detected at several radionuclide monitoring stations in central Europe. After investigation, the International Atomic Energy Agency (IAEA) was informed by Hungarian authorities that <sup>131</sup>I was released from the...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2017-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/17/12677/2017/acp-17-12677-2017.pdf |
| _version_ | 1811267693967310848 |
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| author | O. Tichý V. Šmídl R. Hofman K. Šindelářová M. Hýža A. Stohl |
| author_facet | O. Tichý V. Šmídl R. Hofman K. Šindelářová M. Hýža A. Stohl |
| author_sort | O. Tichý |
| collection | DOAJ |
| description | In the fall of 2011, iodine-131 (<sup>131</sup>I) was detected at several
radionuclide monitoring stations in central Europe. After investigation, the
International Atomic Energy Agency (IAEA) was informed by Hungarian
authorities that <sup>131</sup>I was released from the Institute of Isotopes Ltd. in Budapest, Hungary. It was reported that a total activity of 342 GBq of <sup>131</sup>I was emitted between 8 September and 16 November 2011. In this study, we use the ambient concentration measurements of <sup>131</sup>I to determine the location of the release as well as its magnitude and temporal variation. As the location of the release and an estimate of the source strength became eventually known, this accident represents a realistic test case for inversion models. For our source reconstruction, we use no prior knowledge. Instead, we estimate the source location and emission variation using only the available <sup>131</sup>I measurements. Subsequently, we use the partial information about the source term available from the Hungarian authorities for validation of our results. For the source determination, we first perform backward runs of atmospheric transport models and obtain source-receptor sensitivity (SRS) matrices for each grid cell of our study domain. We use two dispersion models, FLEXPART and Hysplit, driven with meteorological analysis data from the global forecast system (GFS) and from European Centre for Medium-range Weather Forecasts (ECMWF) weather forecast models. Second, we use a recently developed inverse method, least-squares with adaptive prior covariance
(LS-APC), to determine the <sup>131</sup>I emissions and their temporal variation from the measurements and computed SRS matrices. For each grid cell of our simulation domain, we evaluate the probability that the release was generated in that cell using Bayesian model selection. The model selection procedure also provides information about the most suitable dispersion model for the source term reconstruction. Third, we select the most probable location of
the release with its associated source term and perform a forward model
simulation to study the consequences of the iodine release. Results of these
procedures are compared with the known release location and reported
information about its time variation. We find that our algorithm could
successfully locate the actual release site. The estimated release period is
also in agreement with the values reported by IAEA and the reported total
released activity of 342 GBq is within the 99 % confidence interval of the
posterior distribution of our most likely model. |
| first_indexed | 2024-04-12T21:07:11Z |
| format | Article |
| id | doaj.art-6492ed807a2b45cc8fce75cda1509099 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-12T21:07:11Z |
| publishDate | 2017-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-6492ed807a2b45cc8fce75cda15090992022-12-22T03:16:40ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242017-10-0117126771269610.5194/acp-17-12677-2017Bayesian inverse modeling and source location of an unintended <sup>131</sup>I release in Europe in the fall of 2011O. Tichý0V. Šmídl1R. Hofman2K. Šindelářová3M. Hýža4A. Stohl5Institute of Information Theory and Automation, Czech Academy of Sciences, Prague, Czech RepublicInstitute of Information Theory and Automation, Czech Academy of Sciences, Prague, Czech RepublicInstitute of Information Theory and Automation, Czech Academy of Sciences, Prague, Czech RepublicInstitute of Information Theory and Automation, Czech Academy of Sciences, Prague, Czech RepublicNational Radiation Protection Institute, Prague, Czech RepublicNILU, Norwegian Institute for Air Research, Kjeller, NorwayIn the fall of 2011, iodine-131 (<sup>131</sup>I) was detected at several radionuclide monitoring stations in central Europe. After investigation, the International Atomic Energy Agency (IAEA) was informed by Hungarian authorities that <sup>131</sup>I was released from the Institute of Isotopes Ltd. in Budapest, Hungary. It was reported that a total activity of 342 GBq of <sup>131</sup>I was emitted between 8 September and 16 November 2011. In this study, we use the ambient concentration measurements of <sup>131</sup>I to determine the location of the release as well as its magnitude and temporal variation. As the location of the release and an estimate of the source strength became eventually known, this accident represents a realistic test case for inversion models. For our source reconstruction, we use no prior knowledge. Instead, we estimate the source location and emission variation using only the available <sup>131</sup>I measurements. Subsequently, we use the partial information about the source term available from the Hungarian authorities for validation of our results. For the source determination, we first perform backward runs of atmospheric transport models and obtain source-receptor sensitivity (SRS) matrices for each grid cell of our study domain. We use two dispersion models, FLEXPART and Hysplit, driven with meteorological analysis data from the global forecast system (GFS) and from European Centre for Medium-range Weather Forecasts (ECMWF) weather forecast models. Second, we use a recently developed inverse method, least-squares with adaptive prior covariance (LS-APC), to determine the <sup>131</sup>I emissions and their temporal variation from the measurements and computed SRS matrices. For each grid cell of our simulation domain, we evaluate the probability that the release was generated in that cell using Bayesian model selection. The model selection procedure also provides information about the most suitable dispersion model for the source term reconstruction. Third, we select the most probable location of the release with its associated source term and perform a forward model simulation to study the consequences of the iodine release. Results of these procedures are compared with the known release location and reported information about its time variation. We find that our algorithm could successfully locate the actual release site. The estimated release period is also in agreement with the values reported by IAEA and the reported total released activity of 342 GBq is within the 99 % confidence interval of the posterior distribution of our most likely model.https://www.atmos-chem-phys.net/17/12677/2017/acp-17-12677-2017.pdf |
| spellingShingle | O. Tichý V. Šmídl R. Hofman K. Šindelářová M. Hýža A. Stohl Bayesian inverse modeling and source location of an unintended <sup>131</sup>I release in Europe in the fall of 2011 Atmospheric Chemistry and Physics |
| title | Bayesian inverse modeling and source location of an unintended <sup>131</sup>I release in Europe in the fall of 2011 |
| title_full | Bayesian inverse modeling and source location of an unintended <sup>131</sup>I release in Europe in the fall of 2011 |
| title_fullStr | Bayesian inverse modeling and source location of an unintended <sup>131</sup>I release in Europe in the fall of 2011 |
| title_full_unstemmed | Bayesian inverse modeling and source location of an unintended <sup>131</sup>I release in Europe in the fall of 2011 |
| title_short | Bayesian inverse modeling and source location of an unintended <sup>131</sup>I release in Europe in the fall of 2011 |
| title_sort | bayesian inverse modeling and source location of an unintended sup 131 sup i release in europe in the fall of 2011 |
| url | https://www.atmos-chem-phys.net/17/12677/2017/acp-17-12677-2017.pdf |
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